There has been considerable use of balloon angioplasty due to stenosis in arteries having atherosclerotic plaque and the like in an effort to enlarge the lumen and to provide adequate blood flow. While such angioplasty has been successful, it has been found that in many cases restenosis requires that the procedure be repeated.
More recently, there have been efforts at following the balloon angioplasty with placement of a stent, the stent being in the nature of a sleeve that will mechanically maintain some minimum lumen diameter.
It will be obvious that, in order to place a stent utilizing the balloon angioplasty technology, the stent must necessarily have a sufficiently small external diameter to be moved into the desired area by some means such as a catheter, then to be expanded, both to be held in place by the arterial elasticity and to provide the minimum lumen diameter. Prior stents have generally taken the form of wire mesh that is collapsed for placement into the artery, then expanded, either by means of a balloon or by its own elasticity. The stent is generally held in place simply by the arterial elasticity in the first instance, and it has been found that epithelialization takes place throughout the stent so that the entire stent becomes effectively embedded in the vessel wall.
The prior art stents, being woven stainless steel wire or the like tend not to be very flexible longitudinally so that their primary use is in straight portions of vessels. Also, inflation of the balloon is required to expand the wire to its desired size in some cases, while other wire mesh stents tend to take a particular size, and must be held by a sleeve or the like during placement.